Motion Jpeg codec support (not just compression but playback as well) is officially not supported bu OS X 10.7 (Lion). Does anyone know of a workaround? VLC can play movies compressed using Motion Jpeg A in Lion, but not QuickTime Player 7 or X, or the QuickTime web plugin.

We have a large amount of data compressed into movies using this algorithm, and we're hopeful we can convince the Perian team to consider tryoing to add this.

I ran into this same issue. It was the first time I had been disappointed in Apple. Not quite sure I understand why this needed to get dropped. Either way...I found that Handbrake for Mac was able to read the Motion JPEG QTs I had and I could convert them into another format that I could use. Not an optimal solution, but only one I could find.